So the way I understand it is that bathroom receptacles must be on a dedicated circuit, or the bathroom receptacles can include the other outlets in that bathroom if the bathroom is on a dedicated circuit.
Why do they not want bathroom receptacles for example, on the same circuit as the receptacles of an adjacent bedroom? Where is the hazard?
They allow (but do not require) different bathrooms to have a single circuit for the receptacles. I believe they allow it so that only one GFCI receptacle can cover both bathrooms. I think it may be more of an economic solution.
Receptacles from one bathroom may be on the same circuit as ones from another bathroom. As long as nothing else from the bathrooms are on it (lights, heater, fan, etc.).
Or…
Each bathroom can have a dedicated circuit which may include lights and fan or whatever else that’s not recommended to have its own circuit.
Bathrooms, kitchens and other specific areas require branch circuits that “have no other outlets” simply due to their estimated load. Most household circuits will be used for lighting and other low-load components, where these specified areas will generally have higher amperage equipment plugged in at any given time.